Drought? What drought?
Given recent heavy rains why are spring droughts being forecast?
In a week where much of lowland Britain has been on flood alert, many people are at a loss to understand how it is that the Environment Agency is now warning of water shortages next year. Given the November's heavy rains, surely water levels are back to normal now?
Unfortunately, one month of rain does not compensate for a dry period that lasted from February through to October in southern England. It was the second driest year on record since 1921 (surpassed only the legendary summer of 1976). During this dry nine-month spell, there were significant drops in river flows, reservoir storage and groundwater levels across Britain. In the south-east and Thames basin, some rivers were flowing at only 20% of their seasonal average by the end of October. Groundwater levels in the chalk aquifer of southern England are still worryingly low.
Quoted on the Environment Agency website, Barbara Young, Environment Agency Chief Executive, said 'we should not become complacent just because we have had heavy rainfall in the last few days. England and Wales has had an exceptionally dry summer and autumn and while water supplies have provided for us throughout this period and supplies are secure for the coming winter, unless we receive higher than average rainfall between now and March we could be faced with water restrictions and serious water shortages in 2004.' The Environment Agency estimates that it will take around another four weeks of persistent rainfall for river flows and groundwater levels to begin a sustained recovery.
The general principle at work here is, of course, well understood by geography students who have studied the hydrological cycle. However, for large sections of the general population this principle of 'dynamic equilibrium' may be difficult to grasp at first. Essentially, if there is a long period without rainfall, there will have to be an equally long period of rain to restore the deep underground water stores (through percolation) that have kept rivers flowing during the drought.
Back in August, how many people were asking themselves what was keeping their local river flowing, given the lack of rain? As the late autumn rains arrive and groundwater stores and reservoirs begin to be replenished, a great debt is only just starting to be re-paid. Of course, not all rain percolates down into the rocks beneath us a proportion runs over the land too, causing river levels to rise and possibly flood. Hence, we end up in the paradoxical situation where riverline settlements find themselves on flood alert while also anticipating possible hosepipe bans in the spring.
Is your area at risk of flooding?
In an attempt to raise public awareness of flood risk, the Environment Agency recently launched a 24-hour live flood warning service, updated every 15 minutes. The new service also allows homeowners to find out if their property is in an area that is potentially liable to flood.